Digital rights management (DRM), as its name implies, applies to digital media. Digital media encompasses digital audio, digital video, the World Wide Web, and other technologies that can be used to create, refer to and distribute digital “content.” Digital media represents a major change from all previous media technologies. Post-production of digital media is cheaper and more flexible than that of analog media, and the end result can be reproduced indefinitely without any loss of quality. Furthermore, digital content can be combined to make new forms of content. The first signs of this are visible in the use of techniques such as sampling and remixing in the music industry.
Digital media have gained in popularity over analog media both because of technical advantages associated with their production, reproduction, and manipulation, and also because they are sometimes of higher perceptual quality than their analog counterparts. Since the advent of personal computers, digital media files have become easy to copy an unlimited number of times without any degradation in the quality of subsequent copies. Many analog media lose quality with each copy generation, and often even during normal use.
The popularity of the Internet and file sharing tools have made the distribution of digital media files simple. The ease with which they can be copied and distributed, while beneficial in many ways, presents both a security risk and a threat to the value of copyrighted material contained in the media. Although technical control measures on the reproduction and use of application software have been common since the 1980s, DRM usually refers to the increasing use of similar measures for artistic and literary works, or copyrightable content in general. Beyond the existing legal restrictions which copyright law imposes on the owner of the physical copy of a work, most DRM schemes can, and do, enforce additional restrictions at the sole discretion of the media distributor (which may or may not be the same entity as the copyright holder).
DRM vendors and publishers coined the term digital rights management to refer to various types of measures to control access to digital rights, as for example discussed herein, but not limited to those measures discussed herein. DRM may be thought of as a variant of mandatory access control wherein a central policy set by an administrator is enforced by a computer system.
Rights management systems allow a policy to be associated with a document. This policy may be unique for the document or it may be used for multiple documents. If a user wishes to secure a document with permission assignments that are already covered by a set of policies, then a new policy still needs to be defined for this purpose. Also, if many documents are secured using the same policy, but one document needs extra permission assignments, then it is also necessary to define a new policy for that document. This can result in a large number of policies in the system with duplicated rights assignments.